1. Field of the Invention
The present invention relates to a buried type semiconductor optical device having am improved current blocking layer and suitable for use as a semiconductor laser for optical communications for example, and a manufacturing method thereof.
2. Background Art
A buried type semiconductor laser has been used conventionally as one type of a semiconductor optical device. In such a semiconductor laser, an active layer for recombination and light emission is covered with a semiconductor material having a larger energy gap and a lower refractive index than the active layer. The active layer comprises at least an InAlGaAs type semiconductor material and, on both sides of the active layer, an InAlGaAs layer is formed to improve the operational characteristics at high temperature (see, for example, Japanese Laid-open Patent Publication No. 9-129969, page 1 and FIG. 1).
As described above, in a conventional semiconductor optical device, a barrier layer or current blocking layer is formed on both sides of the active layer by use of an InAlGaAs layer to improve the temperature characteristics. However, in this structure, a tip portion of the AlGaAs layer is exposed and oxidized during the manufacturing process. As a result, the cladding layer formed on the InAlGaAs layer may have an undulated surface or defects, which leads to degraded laser characteristics and reduced yield.
The present invention has been devised to solve the foregoing problems in the conventional technique. It is, therefore, an object of the present invention to provide a semiconductor optical device in which oxidation of the InAlGaAs layer as a current blocking layer is prevented to achieve good temperature characteristics and increased yield. The present invention also provides a method for manufacturing the semiconductor optical device having such a structure.